Attempt Number: 3
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
The goal is to stack block 'b' on block 'a', which is currently on block 'c'. Since block 'b' is clear and on the table, we can pick it up and prepare to stack it on 'a'.

New State Description:
The hand is holding block 'b'. Block 'a' is on block 'c' and not clear. Block 'd' is on the table and clear. Block 'c' is supporting block 'a' and not clear.

Action Chosen:
pick-up(b)
